Radiative charge transfer in cold and ultracold Sulfur atoms colliding with Protons

TL;DR

This paper investigates radiative charge transfer in cold and ultracold sulfur-proton collisions using advanced quantum chemistry and scattering methods, providing new cross sections and rate coefficients across a wide temperature range.

Contribution

It introduces the first calculations of radiative charge transfer cross sections and rate coefficients for sulfur atoms colliding with protons at temperatures from 10 μK to 10,000 K.

Findings

Provides cross sections and rate coefficients for sulfur-proton collisions.

Analyzes isotopic effects for H$^{+}$ and D$^{+}$ collisions.

Compares results with other collision systems.

Abstract

Radiative decay processes at cold and ultra cold temperatures for Sulfur atoms colliding with protons are investigated. The MOLPRO quantum chemistry suite of codes was used to obtain accurate potential energies and transition dipole moments, as a function of internuclear distance, between low-lying states of the SH$^{+}$ molecular cation. A multi-reference configuration-interaction (MRCI) approximation together with the Davidson correction is used to determine the potential energy curves and transition dipole moments, between the states of interest, where the molecular orbitals (MO's) are obtained from state-averaged multi configuration-self-consistent field (MCSCF) calculations. The collision problem is solved approximately using an optical potential method to obtain radiative loss, and a fully two-channel quantum approach for radiative charge transfer. Cross sections and rate coefficients are determined for the first time for temperatures ranging from 10 $\mu$ K up to 10,000 K. Results are obtained for all isotopes of Sulfur, colliding with H$^{+}$ and D$^{+}$ ions and comparison is made to a number of other collision systems.